This project aims to develop techniques for minimizing the degree of myocardial injury associated with the use of ischemic arrest during cardiopulmonary bypass. Ischemic arrest is necessary in order to allow the surgeon operating on the heart to perform his manipulations on a bloodless, flaccid, nonbeating, arrested heart. This facilitates repair of cardiac defects and completion of delicate anastomoses. Such cardiac arrest, while diminishing oxygen demand, reduces or eliminates myocardial oxygen supply and substrate replenishment, rapidly causing myocardial ischemia. A well-described technique termed "cardioplegia" has been developed to prevent infarction from occurring during this ischemic process. The present research is designed to improve the cardioplegic preservation of the pigheart model. This heart model has been shown to be closest to the human heart in terms of coronary collateral flow and anatomy. Accordingly, our goal is to improve the cardioplegic preservation of the heart, allowing the heart to recover following the insult of ischemia for prolonged periods of time. During the next year of the grant the project will attempt to evaluate a new approach to cardioplegia termed "high-dose cardioplegia". In addition, an attempt will be made to develop a potassium and hydrogen ion electrode for monitoring myocardial ischemia during cardioplegic arrest. Thirdly, different modalities of preservation, specifically involving calcium channel blockers will be explored in the experimental laboratory, and finally, the use of intermediary metabolites to support the preservation of the heart during the arrest interval will be explored.